Spring powered staplers and staple guns operate by driving a striker with a power spring. The striker ejects a staple by impact blow. In a desktop stapler, the staple is ejected into an anvil of a normally pivotably attached base. Two general principles for spring-actuated staplers are used. In the first design, the striker has an initial position in front of a staple track. The striker is lifted against the force of the power spring to a position above the staple track. The striker is released to impact and eject the staple. This design may be referred to as a “low start” stapler. A second design uses a “high start” position. That is, the striker has an initial position above the staples loaded on the staple feed track. The power spring is deflected while the linked striker does not materially move. At a predetermined position of the power spring deflection, the striker is released to accelerate into and eject a staple.
Typical desktop staplers use a non-spring powered high start design. In such conventional high start designs the striker is driven directly by the handle with no power spring to store energy that could be used to drive the striker. There is further no release mechanism for the striker since the striker simply presses the staples directly under handle pressure.
In conventional high start designs that do use a power spring, the power spring is either unloaded or preloaded in the rest position. Different methods are used to reset the mechanism. U.S. Pat. No. 4,463,890 (Ruskin) shows a desktop stapler with a preloaded spring. Restrainer 42c is an element of the handle and moves directly with the handle. Swiss Patent No. CH 255,111 (Comorga AG) shows a high start staple gun with the handle linked to the power spring through a lever. There is no preload restrainer for the power spring so the spring stores minimal energy through the start of the handle stroke. Both devices use a releasable link or release latch that is positioned behind the striker and de-linked by a direct pressing force from the handle. British Patent No. GB 2,229,129 (Chang) appears to show a high start stapler design. However, no functional mechanism to reset the striker is disclosed. Specifically, no linkage is described to lift the striker with the handle in a reset stroke. The lever 3 resembles a lever used in a low start stapler, but the lever does not lift the striker in any way. Instead, the striker is somehow lifted by a very stiff reset spring, yet no linkage is described to enable a reset spring to lift the striker against the force of the power spring.
Some improvements to a high start stapler are among those disclosed in co-pending U.S. patent application titled “High Start Spring Energized Stapler,” filed on Jan. 20, 2006, Ser. No. 11/343,343, by Joel S. Marks, whose entire contents are hereby incorporated by reference. A high start design may be more compact vertically than a low start design and for this reason may be more preferable for use in a miniature stapler. One reason is that in a high start, typically no lever structure is needed to lift the striker so respective lever engaging slots or features are not needed in the striker. The striker and surrounding housing structure can therefore be of minimal height.
A miniature stapler of any type may be defined as one with an overall length of about three and one half inches or less, having a height of about two and one half inches or less and with a capacity for a one to two inch long rack of staples, equivalent to about 50 to 100 standard desktop staples. However, any stapler that fits less than a full standard four-inch long rack of staples may be considered miniature.
In non-spring actuated type staplers, miniature staplers are known. In a conventional, direct action miniature stapler, the usable pressing area of the handle is about thumb sized. A typical 15 lbs. or more force is required to operate such a direct action stapler to staple through, for example, two or more pages. Needless to say, it is difficult or uncomfortable for a user to apply or squeeze with such force using only a thumb. It is therefore desirable to have a miniature stapler that is suited for squeezing by thumb pressure while requiring a reduced actuation force of less than 15 lbs. For example, a force of 5 to 12 lbs. as measured by a user applying pressure on the handle pressing area is preferred through most of the handle actuation stroke to staple through 2 to 10 pages of paper.